(a) Field of the Invention
The present invention relates to a driving apparatus for a display device. More particularly, the present invention relates to a driving apparatus for a display device that costs less and occupies less area on a printed circuit PCB.
(b) Description of the Related Art
A liquid crystal display (“LCD”) is one of the most widely used flat panel displays. The LCD is composed of two display panels on which field generating electrodes such as pixel electrodes and common electrodes are formed, and a liquid crystal layer interposed between the two display panels. A voltage is applied to the field generating electrodes to generate an electric field in the liquid crystal layer. The orientation of liquid crystal molecules of the liquid crystal layer is determined and the polarization of incident light is controlled through the generated electric field to display an image.
The LCD includes pixels including switching elements, display panels including display signal lines, a gray voltage generator for generating gray reference voltages, and a data driver for generating a plurality of gray voltages. The data driver uses the gray reference voltages to apply gray voltages corresponding to image signals among the generated gray voltages as data signals to data lines among the display signal lines.
Also, among the LCDs, a vertical alignment (“VA”) mode LCD is used in which the longitudinal axes of the liquid crystal molecules are arranged to be perpendicular to the upper and lower display panels in a state where the electric field is not applied. The VA mode LCD is spotlighted since a large contrast ratio and a large reference viewing angle are easily implemented. Here, the reference viewing angle means a viewing angle at which the contrast ratio is 1:10 or a luminance inversion limiting angle among gray levels.
In order to implement an optical viewing angle in the VA mode LCD, a method of forming cutouts in the field generating electrodes and a method of forming protrusions on the field generating electrodes are used. Since the cutouts and the protrusions can determine the directions in which the liquid crystal molecules are inclined, the directions in which the liquid crystal molecules are inclined are dispersed into various directions using the cutouts and the protrusions to increase the reference viewing angle.
However, the VA mode LCD has a problem in that side visibility is inferior to front visibility. For example, in the case of a patterned vertically aligned (“PVA”) mode LCD having cutouts, an image becomes brighter toward a side so that there is no difference in luminance among high gray levels in a severe case and the image looks crumbled.
In order to solve such a problem, each pixel is divided into two sub-pixels and the two sub-pixels are capacitively coupled to each other. A voltage is directly applied to one sub-pixel and a drop in voltage is caused in the other sub-pixel by the capacitive coupling to make the voltages of the two sub-pixels different from each other, and to thus make the transmittances of the two sub-pixels different from each other.
In order to make the transmittances of the two sub-pixels different from each other, data voltages applied to the two sub-pixels must be different from each other, which means that gray voltages applied to the two sub-pixels must be different from each other. The gray voltage generator generates the gray voltages, or the gray reference voltages, to be applied to the two sub-pixels. The gray voltage generator includes a resistor column, switching elements and operational amplifiers mounted on a printed circuit board (“PCB”) together with other driving circuits. However, since the gray voltage generator is composed of separate parts, the gray voltage generator occupies a large area on the PCB and is also expensive.
Therefore a gray voltage generator that can be mounted in a reduced mounting area and having a lower cost is desired, as well as a display device including the gray voltage generator.